Abstract:For grasping fluctuation cycle of Juglans cathayensis populations and forecasting change of the population structure,we conducted a large sample survey on sunny and shady slopes in valley of conservation area in Xinjiang,Using the diameter class structure representing the age structure,we drew up static life table,life expectancy chart,age structure plot,survival curve,and death rate curve chart of J.cathayensis populations.Also,we compared the fluctuation cycle of J.cathayensis populations on different slope aspects by using spectrum analysis method.The results showed that:(1)life expectancies of J.cathayensis populations were fluctuant,both on different slopes of the same age and the same slope of different ages.Life expectancy before 10th age class was higher on sunny slope than that of shady,but after 10th age class it was lower than that of shady slope.(2)J.cathayensis populations on different slope aspects showed increasing age structure.(3)Survival curve of J.cathayensis populations on different slope aspects tended to be Deevey-Ⅱ type,and the survival rate of each age class on sunny slope was higher than that on shady slope.(4)The 1st age plant developed into saplings at the cost of high mortality.The populations in sunny slope had two death peaks in their life history,with the highest peak in 16th age class.However,the shady populations had four death peaks,with the highest peak in 9th age class.(5)Spectrum analysis showed that the quantitative dynamics of J.cathayensis populations were influenced by fundamental wave and also showed obvious small periodic fluctuation,and they had characteristics of multi harmonic superposition that small periodic fluctuation in big one.In the meantime,the small periodic fluctuation of 11th age class was related to high growth characteristic of J.cathayensis,but it might be related to physiological property in 17th age class.